The present invention relates generally to structures for sealing between static members within a gas turbine engine. More particularly, in one embodiment the present invention defines a vane interstage seal assembly for minimizing flow recirculating or leaking between vane stages in a gas turbine engine. Although the present invention was developed for use in a gas turbine engine certain applications may be outside of this field.
Typically, the rotating components within a gas turbine engine include one or more rotors that rotate relative to a static structure. Examples of various types of static members found in a gas turbine engine include vanes, stators, compressor cases, combustors, turbine cases, vane cases, fan cases, diffusers, combustor cases, and other components. Much of the engine's static structure is in fluid communication with the working fluid, or flow path of the engine. As gas flows along the engine flow path, the pressure of the gas typically changes, increasing within the compressor and decreasing within the turbine, and creating a pressure differential that can lead to fluid leakage at connecting points between members of the static structure.
Present gas turbine engine designs often use segmented static members. For example, static members such as vanes may be circumferentially segmented into arcuate pieces, such as doublets or triplets, and axially limited to a single stage of expansion or compression. A vane assembly of this type would therefore have circumferential gaps or cavities between it's components and others of the same stage and axial gaps or cavities between the vane assembly and vane assemblies of other stages. If these gaps, cavities, and passageways are not properly sealed, some amount of gas will recirculate off the flow path and around the static member. This recirculation decreases the efficiency of the compressor or turbine, and lowers the overall efficiency of the engine.
Various apparatus have been proposed for providing seals within gas turbine engines. Examples of seals can be found in the following U.S. Pat. No. 3,754,766 issued to Asplund, U.S. Pat. No. 5,333,995 issued to Jacobs et al., U.S. Pat. No. 4,573,866 issued to Sandy, Jr. et al., U.S. Pat. No. 4,337,016 issued to Chaplin, U.S. Pat. No. 4,529,355 issued to Wilkinson, U.S. Pat. No. 5,188,506 issued to Creevy et al., U.S. Pat. No. 5,562,408 issued to Proctor et al., U.S. Pat. No. 3,518,020 issued to Lake, and U.S. Pat. No. 5,233,824 issued to Clevenger.
Even with the variety of earlier designs, there remains a need for a vane interstage seal assembly in gas turbine engines. The present invention satisfies this need in a novel and unobvious way.